Device for adjusting phase of flat screen

ABSTRACT

A device for adjusting the phase of a flat screen in an automatic flat screen printing machine, which comprises a supporting member for supporting a flat screen, a supporting and driving system for supporting said screen supporting member in such a state that the screen supporting member can be moved in the lengthwise direction of the machine, at least one adjustment screw mechanism for connecting said screen supporting member to said screen supporting and driving system, a phase adjustment driving mechanism for turning said screw mechanism to displace said screen supporting member in the lengthwise direction of the machine.

BACKGROUND OF THE INVENTION

This invention relates to a device for adjusting the phase of a flatscreen in an automatic flat screen dye printing or automatic flat screenprinting machine. More particularly, the invention relates to a devicefor adjusting the phase of a flat screen which can perform the phaseadjustment of a flat screen independently from the screen driving systemand can adjust the phase of a flat screen not only when the printingmachine is stopped but also when the printing machine is in operation.

In conventional automatic printing machines, an endless belt forsupporting and transporting a material to be printed, such as cloth, isfed intermittently and while the endless belt is stopped, a screen isbrought down on the material to be printed, and then, a squeegee memberis scanned on the screen to squeeze out a printing paste on the materialto be printed and the screen and squeegee member are lifted up and theendless belt is fed again.

In this conventional printing method, problems are involved inintermittent feeding of a material to be printed. For example, in orderto register the material to be printed exactly with the screen, it isnecessary to use an expensive printing belt (blanket) which has a muchreduced tendency to elongate and a belt-stopping mechanism having a veryhigh accuracy, and therefore, the structure of the printing machine isinevitably complicated and its price is very high. Further, when aflexible material is printed, an accurate pattern can hardly be printedbecause of a tension given when it is transported.

Recently, as a printing method overcoming the foregoing disadvantages,there has been proposed an automatic screen printing method comprisingfeeding continuously a material to be printed at a constant speed in thelongitudinal direction by means of a transporting member, bringing downa printing stencil (screen), which has been positioned above thematerial to be printed, on the material to be printed to contact thestencil with the material to be printed, moving both the printingstencil and the material to be printed at the same speed in the samedirection, squeezing out a printing paste on the material to be printedwhile the printing stencil travels along a length corresponding to about1/2 of the pattern length, lifting up the printing stencil to releaseits contact with the material to be printed, moving the printing stencilin the reverse direction, and repeating the foregoing operations (seethe specification of U.S. Pat. No. 3,168,036).

This automatic printing method is characterized in that a printingoperation can be performed while a material to be printed is fedcontinuously at a constant speed, but the actual working of thisprinting involves various difficulties. For example, in the automaticscreen printing machine of this type, since a screen frame is alwaysreciprocated in the horizontal direction, precise location of the screenis often difficult.

When the screen is not precisely located, patterns of respective repeatsare made discontinuous or superimposed. Further, when patterns having aplurality of colors are printed, a plurality of screens corresponding tothe number of colors to be printed must be used and in this case,matching of the phases among the screens is very important. If there isa deviation of the phases or relative positions among the screens, aso-called color shear is caused in an obtained print. In the screenprinting machine of the above-mentioned type where a material to beprinted is continuously fed in the printing zone, the phase adjustmentis very difficult and the position or phase of the screen is readilydeviated by the reciprocative movement of the screen, and it is oftendifficult to obtain prints having a precisely registered pattern.

In conventional screen printing machines of the type where a screen isdriven, for example, rotary screen printing machines, a phase adjustmentmechanism is disposed in a screen driving system and the phase of thescreen is adjusted by reducing or increasing the screen driving speed bythis phase adjustment mechanism. However, in printing machines of theabove-mentioned type where a material to be printed is continuously fed,the operation of moving the screen at the same speed as that of thematerial in the same direction as that of the material at the printingstep, the operation of moving the screen in the reverse direction duringthe non-printing period, the operation of scanning the squeegee memberon the screen at the printing step, the operation of contacting thematerial to be printed with the screen at the start of the printing stepand separating the material from the screen at the completion of theprinting step and the operation of continuously feeding the material tobe printed at such a speed that the material is moved along a distancecorresponding to one repeat length while one cycle of the printingoperation is completed must be performed at good timings accordantlywith one another. Accordingly, in the printing machines of this type, itis quite difficult to perform the phase adjustment by a phase adjustmentmechanism disposed in the screen driving system.

OBJECTS OF THE INVENTION

It is therefore a primary object of the present invention to provide adevice for adjusting the phase of a flat screen in a flat screenprinting machine of the type where a material to be printed iscontinuously fed and the printing operation is performed byreciprocating the flat screen in the horizontal direction.

Another object of the present invention is to provide a device foradjusting the phase of a flat screen which can be disposed on a flatscreen supporting member independently from a screen driving mechanismand which can perform the phase adjustment independently from driving ofthe screen.

Still another object of the present invention is to provide a device foradjusting the phase of a screen which can perform the phase adjustmentvery easily not only when the printing machine is stopped but also whenthe printing machine is being operated.

A further object of the present invention is to provide a device foradjusting the phase of a flat screen which has a relatively simplestructure and can be attached to the screen supporting member in arelatively compact form.

SUMMARY OF THE INVENTION

More specifically, in accordance with the present invention, there isprovided a device for adjusting the phase of a flat screen in anautomatic flat screen printing machine, which comprises a supportingmember for supporting a flat screen, a supporting and driving system forsupporting said screen supporting member in such a state that the screensupporting member can be moved in the lengthwise direction of themachine, at least one adjustment screw mechanism for connecting saidscreen supporting member to said screen supporting and driving system, aphase adjustment driving mechanism for turning said screw mechanism todisplace said screen supporting member in the lengthwise direction ofthe machine.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will now be described in detail by reference to theaccompanying drawings, in which:

FIG. 1 is a plan view showing an embodiment of the flat screen phaseadjustment device of the present invention together with a flat screensupporting device and a driving system;

FIG. 2 is a view showing the section of the device of FIG. 1 taken alongthe cross-sectional direction of the machine frame; and

FIG. 3 is a plan view showing an embodiment where the device shown inFIGS. 1 and 2 is used in the state combined with an automatic controlsystem.

DETAILED DESCRIPTION

Referring now to FIGS. 1 and 2, a pair of guide rails 2 are disposed toextend in the horizontal direction along the lengthwise direction of amachine frame 1, and a screen-supporting sliding member 3 is disposedthrough a slide bearing on the guide rails 2 so that it can bereciprocated in the horizontal direction along the guide rails 2. A setof four screen-supporting sliding members 3 corresponding to the fourcorners of a frame 6 supporting a screen 5 are disposed, and two pairsof the screen-supporting sliding members 3a and 3b disposed on both thesides, respectively, are spaced appropriately from screen-drivingconnecting rods 7 and fixed by clamping members 8. The twoscreen-supporting sliding members 3a disposed on the screen advance side(the upper side in FIG. 1) are connected to each other by a connectingrod 9 (see FIG. 2) extending in the cross-sectional direction of themachine frame.

A screen supporting member 10 for supporting the screen frame 6 includesconnecting rods 11a and 11b extending in the cross-sectional directionof the machine frame and connecting rods 12 extending in the lengthwisedirection of the machine frame. Three locating pins 13, 14 and 15 aremounted on the screen supporting member 10 to support the frame 6 in theprecisely located state. The locating pin 13 disposed at the left uppercorner in FIG. 1 is mounted on the front connecting rod 11a by anadjustment piece 16 so that its position can be adjusted in thewidthwise direction. More specifically, a supporting piece 17 having thelocating pin 13 has a female screw to be engaged with a widthwisedirection adjustment screw 18 rotatably mounted on the adjustment piece16, and the supporting piece 17 is pressed in a certain direction by aspring 19. The adjustment piece 16 is fixed to the front connecting rod11a by a bolt 20. In this arrangement, when the widthwise directionadjustment screw 18 is turned, the locating pin 13 is moved in thewidthwise direction and its position can be adjusted. The locating pin14 disposed at the right upper in FIG. 1 is attached to a supportingpiece 21 and this supporting piece 21 is fixed to the front connectingrod 11a by a bolt 20. The locating pin 15 disposed at the left lowercorner in FIG. 1 is attached to a supporting piece 17 and mounted on thelower connecting rod 11b so that its position can be adjusted in thewidthwise direction by means of adjustment piece 16, widthwise directionadjustment screw 18 and spring 19 such as mentioned above. Pin holes 23,24 and 25 corresponding to these locating pins 13, 14 and 15,respectively, are formed on a flange of the screen frame 6. The pin hole23 present at the left upper corner in FIG. 1 is a round hole arrangedto fit the locating pin 13, and the pin hole 24 present at the rightupper corner in FIG. 1 is a long pin hole extending in the widthwise ortransverse direction. The pin hole 25 present at the left lower cornerin FIG. 1 is a long pin hole extending in the lengthwise direction (therepeat direction) of the machine.

In the above arrangement, even if there is a certain dimensional errorin the screen frame 6, the screen frame 6 can be set on the screensupporting member 10 assuredly in the precisely located state. Further,the position of the screen frame 6 in the widthwise direction can alsobe adjusted precisely by the adjustment screws 18.

One of characteristic features of the device of the present inventionresides in that the screen supporting and driving system (screensupporting-sliding members 3a and 3b) and the screen supporting member10 are arranged so that they can make relative movements in thelengthwise direction of the machine and both the members are connectedto each other through the adjustment screw mechanism. This feature willnow be described.

Referring to FIGS. 1 and 2 again, a bracket 26 is fixed to eachscreen-supporting sliding member 3 by suitable clamping means, andbrackets 27 are disposed at the two front corners of the screensupporting member 10 and brackets 28 are disposed at the two lowercorners of the screen supporting member 10. The brackets 27 and 28 fixedto the screen supporting member 10 are placed on the brackets 26 fixedto the screen-supporting sliding members 3 so that the brackets 26 inessence form a carriage. The brackets 27 and 28 are supported by thebrackets 26 so that the position of each of the brackets 27 and 28 isnot changed in either the vertical direction or the cross-sectionaldirection of the machine frame but each of the brackets 27 and 28 can bemoved only in the lengthwise direction of the machine frame. Morespecifically, a roller 30 is mounted on each bracket 26 through a shaft29 extending in the vertical direction and another roller 32 is mountedon the bracket 26 through a shaft 31 extending in the horizontaldirection, so that the roller 30 is engaged with the vertical portionsof the brackets 27 and 28 to set their positions in the cross-sectional(widthwise) direction of the machine and the roller 32 is engaged withgrooves 33 formed on the lower faces of the brackets 27 and 28 to settheir positions in the vertical direction. These rollers 30 and 32 canbe rotated on the shafts 29 and 31, respectively, and accordingly, thescreen supporting member 10 supported through the brackets 27 and 28 isallowed to move only in the lengthwise (repeat) direction of themachine.

In the portion 34 connecting the screen-supporting sliding member 3 andthe connecting rod 9, there is turnably disposed an adjusting screw 35extending in the lengthwise direction of the machine. A female screw 36(see FIG. 1) to be engaged with the adjustment screw 35 is fixed to eachof the brackets 27 mounted on the advance side of the screen supportingmember 10. By this arrangement, the screen supporting member 10 isconnected to the screen-supporting sliding member 3 and is allowed tomake a relative movement in the lengthwise direction of the machineframe by turning of the adjustment screw 35.

The connecting rod 9 for the screen-supporting sliding members 3a has ahollow structure and a connecting shaft 37 is rotatably disposed in theinterior of the rod 9. In both end portions of this connecting shaft 37,namely in the connecting portions 34, bevel gears 38 are fixed and theyare engaged with bevel gears 39 fixed to the adjustment screws 35. Aphase-adjusting geared motor 40 is mounted on one of the connectingportions 34 of the connecting rod 9, and its driving shaft is connectedto one end of the connecting shaft 37.

When the phase-adjusting geared motor 40 is driven in the normaldirection or the reverse direction, the connecting rod 37 is rotated inthe same direction, whereby the adjustment screws 35 are turned in thenormal direction or the reverse direction through the bevel gears 38 and39 and the screen supporting member 10 is advanced or retreated throughthe female screws 36 engaged with the adjustment screws 35 and thebrackets 27. Thus, the phase adjustment of the flat screen can beperformed independently from the reciprocative movement of the screen.

The phase adjustment of the screen can even be performed mannually. Forexample, a knob 41 for manual adjustment is disposed in the engagementportion between the female screw 36 of the bracket 27 and the adjustmentscrew 35. The adjustment can similarly be accomplished by relativelyturning the adjustment screw 35 and the female screw 36 by the knob 41.If such adjustment knobs 41 are arranged, the phase adjustment can beperformed on both the sides independently.

The phase adjustment by driving of the phase-adjusting geared motor 40can be performed automatically during the printing operation by using aphase detecting mechanism and a control mechanism in combination. Thisembodiment will now be described by reference to FIG. 3.

The material 42 to be printed is in the form of a web which is pasted onthe surface of an endless belt 43 by a pasting roller (not shown), andthe material 42 is supported and fed continuously at a constant speed ina certain direction (to the left in the drawings) into printing zones A₁and A₂ by the endless belt 43. At the start of the printing operation, aplurality of flat screens 5 are moved in the same direction (to theleft) as the moving direction of the material 42 at the same speed asthe moving speed of the material 42. At this moment, a squeegee member45 (see FIG. 2) is located at one end of the screen 5 (the left end inthe drawings). A receiving roller 44 (see FIG. 2) disposed below theendless belt 43 is lifted up to the uppermost position to cause thematerial 42 on the endless belt 43 to come into contact with the screen5. In this state, the squeegee member 45 is paired with the receivingroller 44 and they are moved in a direction (to the right in thedrawings) reverse to the moving direction of the material 42 to performprinting on the moving material 42 through the screen 5.

When the squeegee member 45 arrives at the other end (the right end inthe drawings) of the screen 5, the printing operation is completed, andthe receiving roller 44 is lowered, whereby the contact of the material42 with the flat screen 5 is released. The advance of the flat screen 5is stopped and the screen 5 is then moved in a direction (to the rightin the drawings) reverse to the moving direction of the material 42. Thesqueegee member 45 is held by a squeegee supporting mechanism (notshown) is exchanged with a doctor blade (not shown) and the squeegeesupporting mechanism is moved in the same direction as the movingdirection of the material 42, whereby the ink or paste on the screen 5is returned to the printing-starting end. With this movement of thesqueegee supporting mechanism, the receiving roller 44 is moved in thesame direction as the moving direction ofthe material 42 at the loweredposition thereof.

When the squeegee supporting mechanism arrives at one end (the left endin the drawings) of the screen 5, the return course movements of theflat screen 5 and the pair of the squeegee member 45 and the receivingroller 44 are stopped. In this state, the doctor blade is exchanged withthe squeegee member 45 and the receiving roller 44 is lifted up, and theprinting course movement of the screen 5 and squeegee member 45 isstarted. Thus, the foregoing operations are continuously repeated. Inthis automatic screen printing machine of the continuous feed type,during a period from the start of the printing operation to the start ofthe printing operation of the next cycle, the material 42 to be printedis moved by a distance corresponding to the length of one repeat, andthe material 42 can be printed in a continuous manner.

The flat screen positioned in the first printing operation zone A₁ has astencil pattern 46 corresponding to a first color pattern, and thisfirst color pattern 47 is printed on a material 42 to be printed. Theflat screen positioned in the second printing operation zone A₂ has astencil pattern 48 corresponding to a second color pattern, and thissecond color pattern 49 is printed on the material 42 to be printed. Inorder to prevent shears of color patterns, a register mark or indicatingmark 50 is formed on one side of each screen and a correspondingregister mark 51 is formed on the side edge of the material 42. Registermarks 51 formed on the material 42 are spaced from one another atprescribed intervals. The interval between the two adjacent registermarks 51 is equal to the length of one repeat if the timings of therespective operations and the positions of the respective members in theprinting machine are precisely set accordantly with one another. Thephase adjusting mechanism described hereinbefore by reference to FIGS. 1and 2 is mounted on the screen-supporting sliding member in the secondprinting operation zone. A photoelectric detecting mechanism 52 isattached to the connecting rod 9 through a suitable arm 53 to detect orsense the register mark 51 printed on the material 42. Thisphotoelectric detecting mechanism 52 is disposed at such a position thatit detects the register mark 51 only when the flat screen in the secondprinting operation zone is precisely located at the prescribed point. Asignal from the photoelectric detecting mechanism 52 is introduced intoa known control mechanism 54, and power is applied to thephase-adjusting geared motor 40 capable of rotating in the normal andreverse directions through this control mechanism 54.

During the printing step, namely when the flat screen 5 is moved at thesame speed as that of the material 42 in the same direction as themoving direction of the material 42, preferably at the start of theprinting step, the photoelectric detecting mechanism 52 detects theregister mark 51 on the material 42 to cause the control mechanism 54 todrive the phase-adjusting geared motor 40. More specifically, when thereis a positional deviation between the photo-electric mechanism 52 andthe register mark 51, the control mechanism 54 drives the geared motor40 so as to get rid of this deviation. For example, the phase of thescreen 5 in the second printing operation zone A₂ is delayed, the gearedmotor 40 is caused to drive the adjustment screw 35 so that the screen 5supported on the screen supporting member 10 is moved in the directionof advance of the material 42. In contrast, when the phase of the screen5 is put forward, the geared motor 40 is caused to drive the adjustmentscrew 35 so that the screen 5 is moved in the direction reverse to thedirection of advance of the material 42.

As will be apparent from the foregoing illustration, according to thepresent invention, adjustment of the phase of the flat screen can beperformed independently from the screen driving system even while theprinting operation is being conducted by moving the screenreciprocatively in the horizontal direction.

The device of the present invention for adjusting the phase of a flatscreen is especially valuable for an automatic screen printing machineof the type where a material to be printed is continuously fed and theflat screen is moved reciprocatively. However, it will readily beunderstood that the advantage of the present invention that adjustmentof the phase of a flat screen can be performed independently from thescreen driving system even during the printing operation can similarlybe attained even when the present invention is applied to an automaticflat screen printing machine of the type where a material to be printedis intermittently fed into the printing operation zone.

What I claim is:
 1. A flat screen printing machine wherein a web ofmaterial is advanced in a first direction past a printing stationwherein said printing station includes:a printing screen for printing apattern on said web; carriage means for supporting said printing screenabove said web; drive means for moving said carriage means and saidprinting screen at the same speed as said web so that the pattern on theprinting screen can be transferred to said web accurately duringprinting; means for mounting said printing screen on said carriage meanswherein said mounting means includes means allowing relative movementbetween said screen and said carriage means; adjustment means fordriving said screen to move relative to said carriage both with andopposite to the direction of carriage motion; indicating means on saidweb; detector means rigidly mounted with said screen for sensingmisalignment with said indicating means, and motor means activated bysaid detector means to drive said adjustment means until said detectormeans is aligned with said indicating means so that the pattern on saidscreen remains properly aligned with the web during the printingprocess.
 2. The flat screen printing machine of claim 1 wherein theindicating means on said web are a plurality of equally spaced marks andwherein the detector means is a photo-electric device which generates adrive signal when not registered with a mark.
 3. The screen printingmachine of claim 2 wherein the adjustment means includes a screen frameand a pair of screws journalled with respect to the screen frame andthreaded with respect to the carriage wherein when the screw is turnedthe screen is displaced relative to the carriage.
 4. The screen printingmachine of claim 3 wherein the adjustment screws are disposed onopposite sides of the screen and are mutually driven by a shaft whichextends between the screws in a direction normal to the advancement ofthe carriage.
 5. The screen printing machine of claim 4 wherein thecarriage means rests on a pair of parallel tracks and wherein the meansfor mounting the screen includes a bracket with roller means disposedbetween the bracket and carriage to facilitate relative movement as theadjustment screws are rotated.
 6. The screen printing machine of claim 1wherein the means for mounting the screen includes three triangularlyspaced locating pins and wherein the screen includes a screen supportingframe having a hole and two slots therein, in which the pinsindividually register, wherein the hole receives one pin to form a fixedpivot, wherein one of the slots is laterally displaced from the pivotwith respect to the direction of screen motion and extends transverselywith respect to the direction of screen motion and wherein the otherslot is displaced from the pivot in the direction of motion and extendstransversely, and means for adjusting the relative position of lack ofsaid pins to determine the position of the frame accurately.
 7. The flatscreen printing machine of claim 6 wherein the pin forming the pivot ismounted on a threaded support which is moved laterally by a screw andwherein the pin registered with the second slot is mounted on a threadedsupport which is also moved laterally by a screw in order to form themeans for adjusting the relative position of the pins.